1. The Field of the Invention
The present invention is in the field of dental treatment systems that include trays used in applying a dental bleach, fluoride, desensitizing agent, antimicrobial agent, anticariogenic agent, or other dental agents to a person's teeth and/or gums. More particularly, the invention relates to treatment systems that include thin and flexible dental trays that are conformable to a person's teeth when used with a sticky dental treatment composition.
2. The Relevant Technology
Virtually all people desire white or whiter teeth. To achieve this goal, people either have veneers placed over their teeth or have their teeth chemically bleached. In the past, people who desired to have their teeth bleached had to submit to conventional in-office bleaching techniques. The process generally involves: (1) making an alginate impression of the patient's teeth; (2) making a stone cast or model of the impression; (3) vacuum forming a dental tray from the model, usually from a sheet of thin ethyl vinyl acetate (EVA) material, and trimming to exclude gingival coverage. This method results in a tray that is soft and flexible and that is very accurately customized to the patient's teeth. However, the method is time consuming and the resulting tray is relatively expensive.
Because of the high cost of producing custom dental trays, less costly alternatives have been developed. However, these alternatives have substantial disadvantages in terms of accuracy, effectiveness, and comfort of the finished custom tray.
One alternative is the so-called “boil and bite” tray. A relatively thick, non-custom preformed tray (similar to a mouth guard) made of EVA or polyethylene or other material is submerged in boiling water. The preformed tray is relatively thick (e.g., >2 mm) to prevent the tray from collapsing on itself and becoming entirely unusable during the heating process. Upon removal from the heated water, the tray is quickly placed inside a user's mouth. The user bites down and applies contact pressure to make an impression of the biting surfaces of the user's teeth. One problem with “boil and bite” trays is that they are relatively thick and bulky, which make them more intrusive and less comfortable to wear compared to customized trays. The thickness of large, bulky preformed trays also limits the accuracy with which they can be made to conform to the user's teeth and/or gums and makes the trays more rigid.
To the extent that boil and bite trays are made with thinner walls, such trays can be extremely difficult to work with because they tend to shrivel and collapse outside extremely narrow windows of temperature and heating time. For example, if left in a hot water bath too long (i.e., for more than a few seconds) they can quickly become limp and lose their pre-form shape, making it difficult or impossible to conform the tray to the user's teeth.
An alternative to dental trays are strips of a flexible plastic material coated with a bleaching agent that can be applied to a user's teeth. Such strips are placed against the teeth by the user to cover the labial surface of the front 6 teeth and then folded back to cover a portion of the lingual surfaces. Such dental strips can be awkward to place correctly and tend to be easily dislodged. Frequent replacement and refitting of the strips is often required. In addition, they primarily treat only the front surfaces of the teeth and provide little or no treatment of the lingual surfaces of the tooth. Moreover, they provide little or no treatment of the margins between the teeth.
Another alternative is the dual tray assembly disclosed in U.S. Pat. No. 5,616,027 to Jacobs et al. The dual tray assembly is composed of an outer tray that supports or carries an inner tray made of a thermoplastic material comprising EVA. In use, the tray assembly is submerged in hot water to render the inner tray pliable and moldable, while the outer tray remains rigid. The heated assembly is then placed in a patient's mouth to cause the inner tray to take an impression of the patient's teeth. The inner tray results in a final tray that is generally thinner and more comfortable to wear compared to conventional “boil and bite” trays that are sufficiently thick that they do not need a supporting carrier tray. Nevertheless, heating of the tray is still required, and the formed tray must typically be trimmed to yield the finished tray.
In view of the foregoing, there is an ongoing need to develop more comfortable fitting dental trays that can be easily placed over a person's teeth and that will remain in place during the desired treatment time. There is also a need to develop alternatives that are more simple to use but result in a comfortable-fitting tray in order to promote compliance with dental treatment regimes.